Thermoelectric device



April 25, 1950 P. BETZ 2,505,730

THERMOELECTRIC DEVICE Filed March 11. 1946 2 Sheets-Sheet 1 'Jrwe n to aPaul L.Belz.

\f attorneys April 1950 P. L. BETZ 2,55,73

THERMQELECTRIC DEVICE Filed March 11, 1946 2 Sheets-Sheet 2 By (l m/24m.fiz %am Patented Apr. 25, 1950 THERMOELECTRE C DEVICE Paul L. Beta,Baltimore, Md., assignor to Consolidated Gas Electric Light and PowerCompany of Baltimore, Baltimore, Md a corporation of MarylandApplication March 11, 1943, Serial No. 653,494

(ill. 175335) 22 Claims.

This invention relates to thermoelectrically actuated devices, and moreparticularly to improved method and means for effecting the actuation ofsuch devices upon the occurrence of predetermined conditions'whilethermoelectric current is being generated.

Thermoelectrically actuated safety devices are now well known on themarket and are frequently used in systems for controlling the fuelsupply to burners, these devices being of the type that maintain thefuel valve in open position to permit flow of fuel to the burner as longas a con-- stantly burning pilot flame generates thermoelectric currentby heating a thermocouple. On failure of the pilot flame thethermoelectricv current decreases due to the cooling of thethermocouple, and the safety device is thereupon actuated to effect themovement of the fuel valve to its closed position and interrupt the fuelsupply.

In automatic appliances such as water heaters, means are usuallyprovided to prevent the pro- =duction of excessive pressures ortemperatures within the tank if the control system associated therewithfails to shut off the burner when the proper temperature has beenreached, such means flow from the tank or a device employing a,

pressure relief valve which, upon occurrence ofan excessive pressure,opens to relieve the pressure by allowing the contents of the tank toflow out.

It is an object of the present invention to pro-. vide, in associationwith a thermoelectrically actuated safety device, improved means thatwill respond to excessive temperature or pressure conditions within aheated space, such as a tank, oven, or the like, and cause the actuationof the safety device itself to effect closure of the fuel valve uponoccurrence of the conditions deemed dangerous in spite of the fact thatthe pilot flame is continuing in operation and the thermocouple istherefore generating thermoelectric current and supplying the same tothe safety device.

Another object of this invention is to provide a device of the typecharacterized which may be readily adapted to various forms ofthermoelectrically actuated safety devices now on the market.

Another object of this invention is to provide a device of the typecharacterized which may be readily incorporated in thermoelectricallyactuated safety devices that are already installed as well as readilyembodied in such devices when manufactured.

Another object of this invention is to provide a device of the typecharacterized which makes use of alternating current as commonlysupplied for lighting purposes.

Another object of this invention is to provide a device of the typecharacterized which applies to the thermoelectric current generated bythe thermocouple of the safety device a superimposed electric currentthat causes the current in the usual electromagnet or solenoid coil ofthe safety device to decrease to a value such as to effect the actuationof the safety device.

Another object of this invention is to provide improved means foreffecting the actuation of a thermoelectric device upon the occurrenceof predetermined conditions notwithstanding that 'such device isgenerating thermoelectric current.

Another object of this invention is to provide a device of the typecharacterized which is simple and compact in structure, easy to install,and certain and efficient in operation.

Another object of this invention is to provide an improved method foroperating a thermoelectric device upon the occurrence of predeterminedconditions notwithstanding that thermoelectric current is beinggenerated.

Other objects will appear as the description of the invention proceeds.

' The invention is capable of receiving a variety of mechanicalexpressions two of which are illustrated on the accompanying drawings,but it is to be expressly understood that the drawings are for purposesof illustration only, and are not to be construed as a definition of thelimits of the invention, reference being had to the appended claims forthat purpose.

Referring in detail to the accompanying drawings wherein like referencecharacters are employed to designate corresponding parts in the severalfigures:

Fig. 1 is a somewhat diagrammatic elevation of an installation of thepresent invention as applied to the control of a safety deviceassociated with the burner of a water heater;

Fig. 2 is a fragmentary elevation, partly broken away, of the end of thethermocouple leads associated with the body of the safety device;

Fig.3 is a vertical section through an embodiment of the presentinvention;

Fig. 4 is a like view through a second embodiment of the presentinvention; and

Figs. 5 and 6 are electrical diagrams to illustrate the operation of theembodiments shown in Figs. 3 and 4, respectively.

Referring first to Fig. l, the invention is shown somewhat schematicallyas applied to a thermoelectric safety device applied to the gas burnerof a hot water tank, although it is to be expressly understood that theinvention is not limited to such an application, but may be applied tothermoelectrically actuated safety devices associated with the heatersof ovens and other enclosures, or to thermoelectrically actuated relaysor the like, or in fact wherever it is desired to actuate athermoelectric device upon predetermined conditions arising while thethermoelectric current is still being generated. As here shown, the tankID has a burner I l supplied with gas or other suitable fuel throughpipe l2, valve casing 13 and pipe l4. Leading from the valve casing I3is a suitable pipe or tube l for conveying the fuel to a suitable pilotburner l6 whose flame is indicated at l1. Where automatic control ofwater temperature is desired a thermostat (not shown) may be applied totank H), which controls the flow of fuel through pipe l4 and hencecontrols the operation of the burner ll.

Installed within the valve casing I3 is a valve having associatedtherewith a safety device including an electromagent or solenoid forholding the valve in open position as long as said electromagnet orsolenoid is energized by thermoelectric current generated by athermocouple l8 subjected to the pilot flame I1, as disclosed forexample in Patent No. 2,097,838, granted to Sebastian Karrer on November2, 1937. Such safety device may be of any suitable construction, such,for example as may now be found on the market, and as the details of thesafety device constitute no part of the present invention, they have notbeen illustrated except diagrammatically in Figs. 5 and 6 where thethermocouple I8 is shown as connected by leads and 2| to a coil 22 of anelectromagnet or solenoid which would be disposed within the valvecasing I3 in operative relationship with the gas valve therein.

In one type of safety device now on the market the casing l3 carries atits upper end an electrical connector 23 provided with a threaded socketand an insulated terminal such as hereinafter described as provided for'reception of the terminals of the thermcouple leads in embodiments ofthe present invention. The thermocouple may be of any suitableconstruction and, as illustrated in Fig. 2, is shown as having leads ofa well known construction now on the market in the form of a metallictube 24 within which is a concen trically disposed wire 25 provided withinsulation to insulate the same from other metal members. The extremityof tube 24 is flared as shown at 26 to engage the lower face of athreaded nut 21. The end of wire 25 has attached thereto a metal disk28, and interposed between said disk and the flared end 26 of tube 24 isinsulation 29. Nut 21 in the present commercial construction is adaptedto be threaded into the socket of the connector 23 with the disk 28 incontact with the insulated terminal therein whereby'an electricalconnection is made with the coil in the easing 13 and thereby theelectric circuit from the thermocouple 18 to said coil is completed.While for purposes of illustration the invention has been shown asapplied to one form of present kommercial thermoelectrically actuatedsafety device, it is to be expressly understood that the invention isnot limited thereto as it can with equal facility be adapted to anysuitable thermoelectrically actuated safety device as will be apparentto those skilled in the art.

Referring now to Fig. 3 illustrating one embodiment of the presentinvention, a metal body member 30 is provided with an interior chamber3| which is suitably lined with insulating material, as a fiber liner32. One end of chamber 3| is closed by a metallic plate 33 suitably heldin position, as by screws 34, and the opposite end of said chamber isclosed by a plate of insulating material 35 suitably held in position,as by screws 36. At one side said body member 30 carries an electricalconnector similar in-all respects to the end of the thermocouple leadsshown below the line :02: in Fig, 2 and comprising an outer metallictubular member 31 having its end flared at 38 and locked to a threadednut 39 adapted to be. received within the connector 23. Concentricallywithin said tube 31 is a wire 40 insulated from the tubular member 31and connected at its end to a metallic disk-like member 4| withinsulation 42 interposed between said disk and the end 38 of tube 31.The opposite end of tube 31 is suitably retained, as by brazing orsoldering, in a bore hole 43 provided in said body member 30. Bodymember 30 at its opposite side also carries an electrical connector toreceive the thermocouple leads of Fig. 2 and which is identical in allrespects with the construction of the connector 23, comprising aninteriorly threaded sleeve 44 adapted to receive the nut 21, and aterminal 45 adapted to contact the disk 28 and mounted within a cup ofinsulating material 46, said terminal 45 being connected to theextremity of the wire 40 opposite the disk 4|.

Thus when nut 21 is threaded into sleeve 44 and nut 39 is threaded intoconnector 23 the disklike member 28 contacts the terminal 45 and thedisk-like member 4| contacts the terminal in connector 23, whereby anelectrical connection is established from the wire 25 through wire 48-to one terminal of the coil 22 in casing l3 While tubular lead 24 is inelectrical connection with the other terminal of said coil 22 throughnut 21, metallic body member 3!], tube 31 and nut 39. Thereby theelectrical circuit from the thermocouple I8 to the coil 22 in the casing13 is complete with the interposition of u the member shown in Fig. 3between the terminals of the thermocouple leads and the terminals of thecoil leads provided at the connector 23.

In conformity with the present invention means are' provided forimposing an alternating current on the aforesaid thermoelectric circuitjust described. To this end a wire 41 is suitably attached, as bysoldering or brazing, to the wire 40 and at its opposite end wire 41 issuitably attached, as by soldering or brazing, to a lug or connector 48of any suitable construction mounted on the insulating cover plate 35. Asecond lug or connector 49 of any suitable construction is mounted onthe metallic cover plate 33 and con- 80 nected by a'wire 50 to themetallic body member 30, said wire being electrically attached to lug 48and body member 38 in any suitable way as by soldering or brazing.Connectors 48 and 49 are connected by leads 5| and 52 (see Fig. 5) tothe secondary 53 of a transformer 54. The primary 55 of said transformeris connected by leads 56,

51 and 56' to any suitable source of alternating current such as existin the usual house lighting mains and indicated by the terminals 58, 58.

Suitably interposed in the circuit composed of the leads 56 and 51 andcoil 55 is a switch 59 which may be connected for actuation to anysuitable operating means such as a suitable temperature or pressureresponsive device. Thus as shown diagrammatically in Fig. l the switch59 is carried accarao by a member 60 projecting into the interior of thetank In where it may be made to respond to either temperature orpressure within said tank so that, upon occurrence of a predeterminedtemperature or pressure, the switch 59 will be actuated to close thecircuit through the coil E5 and, through the operation of thetransformer 56, an alternating current will be superimposed on thecircuit comprising the thermocouple l8, leads 20 and 2|, and coil 22,the alternating current dividing with part flowing through thethermocouple l8 and part through the coil 22 (see Fig. 5). Thetransformer 54 may be separated physically from or may be mounted on andformed as a unit with body member 30.

Assuming that the pilot i5 is lighted and thermocouple I8 is thussubjected to the heat of the flame, theremoelectric current is generatedby said thermocouple and flows to the coil 22 through the electricalconnections 25, 28, $5, 40, ti, and the terminal in connector 23, on theone hand, and 2d, 21, 44, 35, 31, 39, and the connector 23, on the otherhand. As long as this thermoelectric current is generated the coil 22 isenergized and the fuel valve in the casing i3 is held in open position.Assume now that for some reason the burner H is not shut off when thedesigned maximum temperature in the tank It has been reached. As thethermoelectric current is being generated at the thermocouple l8 thefuel valve is held in open position and will not be actuated by ensuingdangerous conditions. However, when the temperature or pressure in thetank l0, under these assumed conditions, reaches the dangerous conditionat which it is desired that the safety device will close the fuel valve,member 60 responds to close the switch 59 and thereby superimposealternating current through the transformer 54 upon the thermoelectriccurrent flowing in the circuit i8, 2!], 2i, 22 of Fig. 5. Thethermoelectric current is a direct current of predetermined steady valuedepending upon the construction of the thermoelectric circuit. Undernormal conditions when this thermoelectric current decreases in value bya predetermined amount to what may be called the drop value the coil 22releases the fuel valve so as to efiect movement thereof to its closedposition. If now theamplitude of the superimposed alternating currentpassing through coil 22 is greater than the difference between thesteady running value and the drop value of the thermoelectric currentthe superimposed alternating current, compounded with the directthermoelectric current, will cause the current value to pass through andbelow the a drop value of the current in the circuit including the coil22, whereby said coil will no longer be able to retain the fuel valve inopen position and said valve will be released to close and discontinuethe flow of fuel.

The circuit construction of Fig. 3, as shown by the diagram of Fig. 5,employs a parallel arrangement for superimposing the alternating currenton the thermoelectric circuit. The present invention may also beembodied in a construction wherein the alternating current is fed to thethermoelectric circuit by a series arrangement as shown in Fig. 4 andillustrated by the diagram of Fig. 6. Referring to Fig. 4, wherein theparts already described in conjunction with Fig. 3 have the samereference characters as in Fig. 3, the body member 30 now is providedwith a pair of insulating plates 35 and 35' which carry the lugs orother suitable connectors 68 and 69'. Wire 40 is connected to connector48' and is provided 6 with suitable insulation so that it is out ofcontact with the body member 30, it being shown as passing through asmall aperture 32 in the liner 32. In this embodiment, the terminal 45is connected to the connector M bya wire 63 which is also suitablyinsulated from body member 30. If leads 5| and 52' are now connected tothe connectors Q8 and 69, following the circuit diagram of Fig. 6, thealternating current in the secondary 53 will be applied to thethermoelectric circuit in series with the thermocouple i8 and the coil22, and the closure of the valve will occur as heretofore described inconjunction with the embodiments of Figs. 3 and 5.

With the series arrangement, a second transformer, which may also bemounted on or made in unitary relation with the body member 30, ispreferably interposed between the secondary 53 and the points ofconnection of the alternating current circuit to the thermoelectriccircuit. As shown in Fig. 6, the circuit of secondary 53 includes theprimary 6% of a second transformer 65 whose secondary 66 is connected tothe connectors t8 and d9 in the thermoelectric circuit and is in serieswith the thermocouple I8 and coil 22. The transformer 65 should have alow ratio of transformation, having relatively few turns in thesecondary 56, in order that its resistance may be small as compared withthe resistance of the coil 22. However, if preferred, the transformer 65may be omitted and the leads 5! and 52 from coil 53 may be attacheddirectly to the connectors 48' and 69' as previously indicated.

It will therefore be perceived that the present invention provides asimple, compact and easily installed device which may be readily adaptedto any suitable form of thermoelectrically actuated safety device forapplication to such devices as are already installed or forincorporation therein when manufactured, the device providing atemperature or pressure responsive safety feature that will effect theactuation of the thermoelectric safety device itself, notwithstandingthat thermoeiecric current is being generated, and assure closure of thefuel valve, or the actuation of any other suitable element, upon theoccurrence 'of the predetermined conditions considered dangerous. Theinvention also provides an eflicient means for actuating any suitablethermoelectric device when predetermined conditions arisenotwithstanding the generation of the thermoelectric current.

While the embodiments of the invention illustrated on the drawings havebeen described with considerable particularity, it is to be expresslyunderstood that the invention is not limited thereto as will now beapparent to those skilled in the art. While the invention has beenillustrated as applied to a hot water tank it will be apparent to thoseskilled in the art that it may be applied to any other suitablethermoelectric device that is to be actuated upon the arising ofpredetermined conditions while thermoelectric current is beinggenerated. While for purposes of illustration the invention has beenshown as applied to one known form of commercial thermoelectricallyactuated safety device, it will be apparent that the invention can beadapted to any suitable device of this character. Changes may also bemade in the details of construction and arrangement of parts, partsillustrated may be replaced by equivalent parts, etc., without departingfrom the spirit of this invention. Reference is accordingly to be had tothe appended claims for a definition of the convention.

What is claimed is:

1. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a circuit connected tosaid thermoelectric circuit, a source of alternating current ofsubstantially constant value connected to said second named circuit, andmeans associated with said source for energizing said second namedcircuit on the occm-rence 01 a predetermined condition.

2. In a thermoelectric device or the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means i'or superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a second circuitconnected in parallel to said thermoelectric circuit, a source ofalternating current of substantially constant value connected to saidsecond circuit, and means associated with said source .ior energizingsaid second circuit upon the occurrence of a predetermined condition.

3. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a second circuitconnected in series with said thermoelectric circuit, a source ofalternating current of substantially constant value connected to saidsecond circuit, and means associated with said source for energizingsaid second circuit upon the occurrence of a predetermined condition.

4. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a transformer having itssecondary connected to said thermoelectric circuit, a source ofalternating current of substantially constant value in circuit with theprimary of said transformer, and means associated with said source forenergizing the circuit of said primary on the occurrence of apredetermined condition.

5. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a transformer having itssecondary connected in parallel to said thermoelectric circuit. a sourceof alternating current of substantially constant value in circuit withthe primary of said transformer, and means in the circuit of saidprimary for closing said circuit upon the occurrence of a predeterminedcondition.

6. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially" constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a transformer having itssecondary connected in' series with said thermoelectric circuit, asource of alternating current of substantially constant value in circuitwith the primary of said transformer, and means in the circuit of saidprimary for closing said circuit upon the occurrence of a predeterminedcondition.

'7. In a thermoelectric device of the type including a thermocouple, athermoelectric circuit connected thereto and a coil in saidthermoelectric circuit, means for superimposing an alternating currentof substantially constant value on said coil in said thermoelectriccircuit for actuation of said device while thermoelectric current isbeing generated at said thermocouple comprising a transformer having asecondary of few turns and low resistance connected to saidthermoelectric circuit, a second transformer having its secondaryconnected to the primary of said first named transformer, a source ofalternating current of substantially constant value in circuit with theprimary of said second named transformer, and means in the circuit ofsaid last named primary for closing said circuit upon the occurrence ofa predetermined condition.

8. In a thermoelectric device of the type including a thermocouple and acoil in circuit therewith, means for superimposing an alternatingcurrent on the coil in said thermoelectric circuit for actuating saiddevice while said thermocouple is generating thermoelectric currentcomprising a member adapted to be interposed physically and electricallybetween the terminals of said thermocouple and the terminals of saidcoil and having pairs of electrical terminals for cooperating with theterminals of said thermocouple and with the terminals of said coil,respectively, said member also having electrical connections in circuitwith the aforesaid pairs of electrical terminals adapted to be connectedin circuit with a source of alternating current, and a switch associatedwith said source for energizing said last named circuit on theoccurrence of a predetermined condition.

9. In a thermoelectric device of the type including a thermocouple and acoil in circuit therewith, means for superimposing an alternatingcurrent on the coil in said thermoelectric circuit for actuating saiddevice while said thermocouple is generating thermoelectric currentcomprising a metal body member adapted to be interposed physically andelectrically between the thermocouple and the coil and provided withterminal connections for one of the leads of the thermo couple and oneof the leads of said coil, an electrical connection insulated from saidmetal member and provided with terminals for connection to the otherlead of said thermocouple and the other lead of said coil, a pair ofconnectors carried by said body member for connection to a source ofalternating current and respectively connected to said body member andsaid electrical connection, and a switch associated with said source forenergizing the circuit including said connectors upon the occurrence ofa predetermined condition.

10. In a thermoelectric device of the type imcluding a thermocouple anda coil in circuit theretions for attachment to one of the leads of saidthermocouple and one of the leads of said'coil, a pair of connectorshaving electrical connections for attachment to the other lead of saidthermocouple and the other lead of said coil and adapted to be connectedin circuit with a source of alter- I nating current, and a switchassociated with said source for energizing said last named circuit uponthe occurrence of a predetermined condition.

11. In a device for superimposing alternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated, a metallic body member provided withelectrical connectors adapted to be connected to the thermocouple leadsand the coil leads of the thermoelectric circuit, and a pair ofconnectors carried by said body member for connection with a source ofalternating current, said last named connectors being electricallyconnected with said first named connectors to superimpose thealternating current on the thermoelectric current ln said coil when thecircuit through said second named connectors is supplied withalternating current.

12. In a device for superimposing alternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated, a metallic body member provided withconnectors for attachment to a thermocouple lead and a coil lead, anelectrical connection carried by said body member for attachment to theother thermocouple lead and the other coil lead, and a pair ofconnectors carried by said body member and respectively connectedelectrically to said body member and said connection, said second pairof connectors adapted to be connected with a source of alternatingcurrent to superimpose the alternating current on the thermoelectriccircuit in said coil when the circuit through said last named connectorsis supplied with alternating current.

13. In a device for superimposing alternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated, a metallic body member provided withconnectors for attachment to a thermocouple lead and a coil lead, and apair of connectors carried by said body member and having connectionscarried by said body member for respective attachment to the otherthermocouple lead and the other coil lead, said second pair ofconnectors adapted to be connected to a source of alternating currentfor superimposing alternating current on the thermoelectric circuit insaid coil when the circuit through said last named connectors issupplied with alternating current.

14. In a device for superimposing alternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated, a metallic body member provided withconnectors for attachment to the thermocouple leads and the coil leadsof the thermoelectric circuit, a pair'of connectors carried by said bodymember for connection with a source of alternating current, said lastnamed connectors being electrically connected with said first namedconnectors to superimpose the alter- Y nating current on thethermoelectric current in said coil when the circuit through said secondnamed connectors is supplied with alternating current, and a transformercarried by said body member through which the alternating current issupplied to said last named connectors.

15. In a device for superimposing alternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated,- a metallic body member provided withconnectors for attachment to the thermocouple leads and the coil leadsof the thermoelectric circuit, a pair of connectors carried by said bodymember for connection with a source of alternating current, said lastnamed connectors being electrically connected with said first namedconnectors to superimpose the alternating current on the thermoelectriccurrent in said coil when the circuit through said second namedconnectors is supplied with alternating current, and a transformercarried by said body member and connected in parallel through said lastnamed connectors with said thermocouple and coil leads.

'16. In a device for superimposingalternating current on a coil in athermoelectric circuit for actuation of the latter while thermoelectriccurrent is being generated, a metallic body member provided withconnectors for attachment to the thermocouple leads and the coil leadsof the thermoelectric circuit, a pair of connectors carried by said bodymember for connection with a source of alternating current, said lastnamed connectors being electrically connected with said first namedconnectors to superimpose the alternating current on the thermoelectriccurrent in said coil when the circuit through said second namedconnectors is supplied with alternating current, and a transformercarried by said body member and connected in series through said lastnamed connectors with said thermocouple and coil leads.

1'7. The method of actuating a thermoelectric device upon the occurrenceof a predetermined condition notwithstanding the generation ofthermoelectric current which includes the step of imposing on thethermoelectric circuit an alternating current the peak value of which issubstantially constant and is greater than the difference between thesteady running value of the thermoelectric current and the current valueat which the thermoelectric device is operated upon decrease in thegeneration of thermoelectric current.

18. The method of operating a thermoelectric device to cause said deviceto function on a, predetermined condition notwithstanding the continuedgeneration of thermoelectric current which comprises connecting thethermoelectric circuit which includes a thermocouple and anelectromagnet winding with a source of alternating current the peakvalue of which is substantially constant and is greater than thedifference between the steady running value of the thermoelectriccurrent and the current value at which the device is actuated upondecrease of the thermoelectric current to compound the alternating andthermoelectric currents and cause the current in the said electromagnetwinding to decrease below said last named value upon the occurrence ofsaid predetermined condition.

19. In a, thermoelectric device of the type including a, thermocoupleadapted to be subjected to a source of heat and a device including acoil 7s in circuit with said thermocouple adapted to operate upon a.predetermined decrease in the thermoelectric current generated at saidthermocouple, means for actuating said device while said thermocouple isgenerating thermoelectric current including means adapted to beinterposed physically and electrically between the thermocouple and thecoil for connecting a source of alternating current to the coil in saidthermoelectric circuit and a switch for closing said circuit includingsaid source of alternating current to superimpose the alternatingcurrent on the thermoelectric current in the coil in said thermoelectriccircuit. said switch being provided with means responsive to the;occurrence of a predetermined condition.

20. A device forconnecting the thermocouple and solenoid coil of athermoelectric safety device comprisinga body member having elementsforming terminals for one of the leads of the thermocouple and one ofthe leads of the coil, said terminals being electrically connected toone another, means carried by and insulated from the terminal-formingelements of said body member and forming electrically connectedterminals for connection to the other lead of said thermocouple and theother lead of said coil, 2. pair of connectors carried by said bodymember for connection to a source of alternating current, and means forelectrically connecting one of said pair of connectors to one of theleads of the thermocouple and the other connector to one of the leads ofthe coil.

21. A device for connecting the thermocouple and solenoid coil of athermoelectric safety device comprising a metallic body member havingelements forming terminals for one of the leads of the thermocouple andone of the leads of the coil, said terminals being electricallyconnected to one another through said body member, a

conductor housed within and insulated from said body member and havingterminals for connection to the other lead of said thermocouple and tieother lead of said coil, 9. pair of connectors carried by said bodymember for connection to a source of alternating current, one of saidconnectors being insulated from said body member and the other beingelectrically connected thereto, and means for electrically connectingsaid insulated connector to said conductor.

22. A device for connecting the thermocouple and solenoid coil of athermoelectric safety de-' vice comprising a metallic body member havingelements forming terminals for one of the leads of the thermocouple andone of the leads of the coil, said terminals being electricallyconnected to one another through said body member, means 7 carried byand insulated from said body member forming terminals for connection tothe other lead of said thermocouple and the other lead of said coil, apair of connectors carried by and insulated from said body member forconnection to a source of alternating current, and means forelectrically connecting said pair of connectors to the terminal-formingmeans carried by said body member.

PAUL L. BETZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,029,974 Burnham June 18, 19122,276,909 Alfery Mar. 17, 1942 2,296,764 Braden Sept. 22, 1942 2,340,234Thornbery et a1. Jan. 25, 1944

